The “Image Selection” will default to “Random” in case you have set “Select an Image” to either “At each browser session” or “On a page reload”, because it does not track which image has been displayed.

After selecting the “Full Screen” option, you should see the “Background Transitioning Effect” area, which allows you to select a slider or other transition effect, including its speed.

Regarding the image selection and transition order, is it possible for the initial image to be random, but then transition in sequential order? For example, if you have 4 images, it could load image #2 by random selection, the slideshow would then go in order to #3 > #4 > #1 etc. This way there could be a different stating image each time, but also the entire set would display before there is a repeat.